1. Field of the Invention
The present invention relates generally to a hermetic compressor or a closed-type compressor for use in, such as, a refrigerator.
2. Description of the prior Art
Recently, hermetic compressors with reduced noise have been largely demanded in view of the environmental amenity. In order to satisfy such demands, there has been proposed a hermetic compressor having a hermetic or sealed casing of such a shape as to prevent generation of a resonance sound in the sealed casing, as disclosed such as in Japanese Second (examined) Patent Publication No. 3-53476.
Specifically, the proposed conventional sealed casing has a shape such that a straight line drawn from any portion of its inner wall at a right angle intersects with an opposite portion of the inner wall at an angle other than the right angle. This structure serves to prevent generation of resonance in the sealed casing since an acoustic or sound wave reflected by the opposite inner wall portion does not return to the portion where it comes from. Accordingly, this structure serves to prevent increment of the noise which would be otherwise caused by the resonance in the sealed casing, so as to provide the hermetic compressor with reduced noise.
However, the foregoing conventional structure has the following drawbacks:
Specifically, according to the conventional structure, as an angle between the above-noted straight line and the opposite inner wall portion deviates from the right angle by a larger degree, the effect for preventing the generation of resonance in the sealed casing becomes lager. However, in order to provide a larger deviation from the right angle for enhancing such an effect, a shape of the sealed casing has to be distorted unnaturally. As a result, the sealed casing is weakened in strength, which causes increment of the noise caused by vibration of the sealed casing. In addition, since the shape of the sealed casing is forced to be distorted in view of reducing the resonance noise, the space in the sealed casing can not be effectively utilized in comparison with a sealed casing having a normal shape. As a result, the sealed casing undesirably increases in size for accommodating therein a compressing unit and a driving unit which drives the compressing unit.